Because of evidence that knowledge of immunology and possible immunopathology of the gingiva may be essential to an understanding of the pathogenesis of periodontal disease, this project will conduct investigation into: 1) the presence in gingiva from subjects with periodontitis of potential antigens derived from dental plaque; 2) the possibility of such antigens existing as immune complexes; 3) the possible presence in gingiva of antibody to extracts of dental plaque microorganisms. Immunohistochemical technics will comprise the primary methodology of investigation.